Did you know the UC Master Gardener Program of San Joaquin County has been part of a National Rose Trial since 2018? The National Rose Trial is part of the American Rose Trials for Sustainability (A.R.T.S.) Program which has trial sites across the United States. The National Rose trial was initiated in 2012 by individuals representing multiple rose stakeholder groups including: private industry, the scientific community, and public gardens.

Since 2018, UC Master Gardeners in San Joaquin County have been part of a National Rose Trial. The trial is part of the American Rose Trials for Sustainability program, which aims to identify roses that perform well in a given region when grown under “minimal input conditions.” (Photo: Marcy Sousa)

The goal of the A.R.T.S. program is to identify roses that perform well in a given region when grown under "minimal input conditions."  What are "minimal input conditions?" 

• there are no pesticides used
• we do not deadhead the flowers
• there is no pruning (except to remove winter-killed canes in the spring, or those killed by rodents)
• we do not add any fertilizer (only compost is added prior to planting)
• plants are not covered in the winter (in colder climates it is common to cover and protect roses)

A.R.T.S. national test sites are strategically located throughout the U.S. and are hosted by partners that share the A.R.T.S. mission including botanical gardens, arboreta, municipalities, colleges and universities. There are only two Mediterranean climate trial locations and they are both located in California.  The National Rose Trials at the UC Cooperative Extension office in San Joaquin County began in 2018, and the second location at Fullerton Arboretum started in 2019.

Rose bushes in full bloom, outside of the UC Cooperative Extension Office in San Joaquin County (Photo: Marcy Sousa)

A.R.T.S. defines its climate regions using the Köppen climate classification system, which is the preferred means used by ecologists. This system not only takes into account temperature, but also seasonal precipitation and humidity. The A.R.T.S. evaluation protocol has 45% of the score reflecting sub-components of the health and quality of the foliage, 42.5% the presentation and quality of the flowers and 12.5% reflecting the plant's growth habit. Climate can greatly impact all three of these evaluation categories.

How does the trial work?

Karrie Reid, UC ANR Environmental Horticulture Advisor, has been managing and overseeing the trial since its inception in 2018. Roses were planted in an unused turf area that was converted to rose trial grounds.  One of the selling features of converting the turf sections was the calculated water savings - 3,656 sq. ft. of turf used more than 103,000 gallons of water, while 60 roses in the same area on drip irrigation uses approximately 6,175 gallons, a huge 94% savings! 

Each year starts the beginning of a new trial with 20 difference rose cultivars. Three of each rose variety is planted randomly throughout the beds, allowing ample spacing between plants to observe natural plant habit. Mixed in the plantings are two standard rose varieties known to perform well and to be disease resistant. The trial runs for two years, evaluations start the year of planting and finish the following year so roses only go through one winter season. There are two staggered rose trials planted in San Joaquin County per year.

Roses being tested in the A.R.T.S. trial may be watered thoroughly during the first year after planting for proper establishment during the season they were planted. The roses in the UC Master Gardener of San Joaquin trial are watered 1-inch, twice a week while they are blooming during the first year, and only once a week during the second year.

Each rose is evaluated monthly during the growing season; the roses are rated on a 10-point scale, judging them for their foliage, flowers and plant form. (Photo credit: Marcy Sousa)

Each rose is evaluated twice monthly during the growing season by a team of UC Master Gardener volunteers, the local advisor, or a local rose club member. Evaluators rate the roses on a 10-point scale, judging on foliage, flowers and form. The evaluation data collected is submitted to the A.R.T.S. program for evaluation.

UC Master Gardeners of San Joaquin County, Kate Vizcarra and Janet Nimtz, evaluate roses for its foliage, flowers and form. (Photo Credit: Marcy Sousa)

Picking the winners

Any rose cultivar in a given region that scores higher than the average of the standard cultivars and has greater than a 50% survival is given the A.R.T.S. Local Artist Award. Any rose that receives the A.R.T.S. Local Artist award in four or more regions is given the A.R.T.S. Master Rose Award.

Having the A.R.T.S. awards in different regions means that nursery and landscape professionals along with home gardeners can be sure they are selecting plants that will perform well in their gardens. Not every plant is going to thrive in every climate. While a particular cultivar may do well in the short, cool growing season of Maine, it may perform very poorly in the much longer and warmer conditions found in California.  

We are excited about the opportunity to participate in the program and are eager to find out the winners in our region. Follow us on Facebook @ucsjmg to hear about the winners from us.

Soon, the UC Master Gardener Program in San Joaquin County will begin prepping the ground to install a brand new trial in January 2020!

If you would like to learn more about the A.R.T.S. program, visit their website: https://www.trustedroses.com. If you have a gardening related question, you can contact the UC Master Gardeners at 209-953-6112. More information can be found on our website: ucanr.edu/sjmg.

Information for this article was taken from the A.R.T.S. website and Nursery Management magazine.